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How Sugar Makes Us Age - Protein Cross-Linking and Aging

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Updated March 16, 2008

What is Cross-Linking?:

When you heat onions or toast bread, the sugar molecules bond to protein molecules. This bonding, which in cooking is called carmalization, is a result of the sugar molecules attaching to protein molecules. When this happens, a series of reactions occur (called glycation) that result in protein molecules bonding to each other.

This Happens in My Body?:

Chemically speaking, yes. The process is slow and complicated, but over time more and more protein molecules are cross-linked. These cross-linked molecules don't function propoerly. When enough cross-linked molecules accumulate in a specific tissue (such as cartilage, lungs, arteries and tendons), there can be a change in function.

What Changes With Cross-Linking?:

Basically, things become stiffer. When tissues stiffen, they do not function as efficiently. Many of the symptoms of aging have to do with the stiffening of tissues. Cataracts, for example, are a stiffening of your eyes' lenses.

Can I Stop It?:

No, but you can slow it down. Researchers believe that if the concentration of sugar in the blood is high, then more cross-linking occurs. Everyone could benefit from keeping their blood sugar from spiking. Foods with a high glycemic index, such as sugary sodas and juices, release sugar into the body quickly. These foods have been associated with cardiovascular disease, possibly because of protein cross-linking.

More on Why We Age

Sources: Aging Under the Microscope; National Institutes of Health, National Institute of Aging.

Sugar and Cardiovascular Disease Circulation. 2002;106:523.

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